| 摘要 |
<p>PURPOSE:To prevent a shift of a focus when a ceramic coated substrate is used as a photomask by specifying the thickness of a ceramic film formed on one side of a silicon substrate of a specified thickness and forming a ceramic film having the same quality on the other side by chemical vapor deposition in a specified thickness. CONSTITUTION:A ringlike silicon substrate 11 is coated with at least one of silicon carbide and silicon nitride by chemical vapor deposition to form a ceramic film 12. The pref. thickness of the substrate 11 is 100-1,000mum. The ceramic film 12A formed on one side of the substrate 11 is 0.1-20mum and the ceramic film 12B formed on the other side is made 0.85-1.15 times as thick as the film 12A. The curving of the silicon substrate due to the difference between the coefft. of thermal expansion of the substrate and that of the ceramic film is inhibited, the flatness of the substrate can be ensured and a shift of a focus can be inhibited when the ceramic coated substrate is used as a photomask at the time of drawing an electronic circuit on a semiconductor wafer.</p> |
